1. Field
The present invention relates to a light emitting module, and more particularly, to a lens for surface illumination and a light emitting module for surface illumination including the same.
2. Discussion of the Background
A light emitting module for back lighting a liquid crystal display or a light emitting module for surface illumination used in a luminaire for surface illumination generally includes light emitting devices mounted on a circuit board, and a lens which disperses light emitted from light emitting devices at a wide angle. The light emitted from the light emitting device is uniformly dispersed through the lens, thereby allowing uniform illumination of a wide area using a small number of light emitting devices.
FIG. 1a and FIG. 1b are a schematic sectional view and a schematic perspective view of a typical light emitting module and a typical lens in the art, respectively.
Referring to FIG. 1a and FIG. 1b, the light emitting module includes a circuit board 100, a light emitting device 200, and a lens 300. The circuit board 100 is a printed circuit board on which a circuit is formed to supply power to the light emitting device 200.
The light emitting device 200 generally includes a light emitting diode chip 210, a molding member 230 covering the light emitting diode chip 210, and a package substrate 250. The molding member 230 includes phosphors for wavelength conversion of light emitted from the light emitting diode chip 210, and may have a lens shape. The package substrate 250 may have a recess on which the light emitting diode chip 210 is disposed. The light emitting device 200 is electrically connected to the circuit board 100.
The lens 300 includes a lower surface 310 and an upper surface 350, and may include a flange 370 and legs 390. With the legs 310 of the lens attached to an upper side of the circuit board 100, the lens 300 is disposed above the light emitting device 200. As shown in FIG. 1b, the lens generally includes three legs 310 disposed at apexes of an equilateral triangular shape.
The lens 300 has a light incident surface 330 through which light emitted from the light emitting device 200 enters the lens 300, and a light exit surface 350 through which the incident light exits. The light incident surface 330 is an inner surface of an artillery shell-shaped concave section 320 formed on the lower surface 310 of the lens 300. Since the concave section 320 is disposed above the light emitting device 200, the light emitted from the light emitting device 200 enters the lens 300 through the light incident surface 330. The light exit surface 350 allows the light entering the lens 300 to exit the lens at a wide beam angle therethrough.
A typical light emitting module can realize uniform light over a wide area by allowing light emitted from the light emitting device 200 to be dispersed through the lens 300. However, since the light emitting device 200 mounted on the circuit board 100 employs the package substrate 250, the light emitting device 200 has a relatively large size. As a result, the concave section 320 for forming the light incident surface 330 of the lens 300 has a relatively large entrance and a relatively great height, thereby making it difficult to obtain a slim structure of the lens 300. Moreover, since the light emitted from the light emitting device 200 has a relatively narrow beam angle, there is a limit in dispersion of the light through the lens 300.
Moreover, since the light emitting device 200 is disposed below the lower surface 310 of the lens 300, some of light emitted from the light emitting device 200 does not enter the lens 300 and can be lost below the lower surface of the lens 300.